Obesity is a common condition and a major public health problem in developed nations including the United States of America. As of 2009, more than two thirds of American adults, approximately 127 million people, were either overweight or obese. Data suggest that 300,000 Americans die prematurely from obesity-related complications each year. Many children in the United States are also either overweight or obese. Hence, the overall number of overweight Americans is expected to rise in the future. It has been estimated that obesity costs the United States approximately $100 billion annually in direct and indirect health care expenses and in lost productivity. This trend is also apparent in many other developed countries.
For adults, the body mass index (BMI) is used to determine if one is overweight or obese. A person's BMI is calculated by multiplying body weight in pounds by 703 and then dividing the total by height in inches squared. A person's BMI is expressed as kilograms per meter squared. An adult is considered overweight if his or her BMI is between 25 and 30 kg/m2. Obesity is defined as possessing a BMI between 30 and 40 kg/m2. A BMI greater than 30 kg/m2 is associated with significant co-morbidities. Morbid obesity is defined as possessing either a body weight more than 100 pounds greater than ideal or a body mass index (BMI) greater than 40 kg/m2. Approximately 5% of the U.S. population meets at least one of the criteria for morbid obesity. Morbid obesity is associated with many diseases and disorders including, for example: diabetes; hypertension; heart attacks; strokes; dyslipidemia; sleep apnea; pickwickian syndrome; asthma; lower back and disc disease; weight-bearing osteoarthritis of the hips, knees, ankles and feet; thrombophlebitis and pulmonary emboli; intertriginous dermatitis; urinary stress incontinence; gastroesophageal reflux disease (GERD); gallstones; and, sclerosis and carcinoma of the liver. In women, infertility, cancer of the uterus, and cancer of the breast are also associated with morbid obesity. Taken together, the diseases associated with morbid obesity markedly reduce the odds of attaining an average lifespan. The sequelae raise annual mortality in affected people by a factor of 10 or more.
Current treatments for obesity include diet, exercise, behavioral treatments, medications, surgery (open and laparoscopic) and endoscopic devices. New drug treatments for obesity are currently being evaluated in clinical trials. However, a high efficacy pharmaceutical treatment has not yet been developed. Further, short-term and long-term side effects of pharmaceutical treatments often concern consumers, pharmaceutical providers, and/or their insurers. Generally, diet or drug therapy programs have been consistently disappointing, failing to bring about significant, sustained weight loss in the majority of morbidly obese people.
Currently, most operations used to treat morbid obesity include lap band surgery or gastric restrictive procedures, involving the creation of a small (e.g., 15-35 ml) upper gastric pouch that drains through a small outlet (e.g., 0.75-1.2 cm), setting in motion the body's satiety mechanism. About 15% of operations used to treat morbid obesity performed in the United States involve combining a gastric restrictive surgery with a malabsorptive procedure. Typical malabsorptive procedures divide small intestinal flow into a biliary-pancreatic conduit and a food conduit. Potential long-term complications associated with abdominal surgical procedures include herniation and small bowel obstruction. In addition, long-term problems specific to bariatric procedures also include gastric outlet obstruction, marginal ulceration, protein malnutrition, and vitamin deficiency.
Other surgical strategies for treating obesity include endoscopic procedures, many of which are still in development. Endoscopically placed gastric balloons restrict gastric volume and result in satiety with smaller meals. Endoscopic procedures and devices to produce gastric pouch and gastrojejunal anastomosis to replicate laparoscopic procedures are also in development. These procedures, however, are not without risks.
Gastro-esophageal reflux disease (GERD) is another common health problem and is expensive to manage in both primary and secondary care settings. This condition results from exposure of esophageal mucosa to gastric acid as the acid refluxes from the stomach into the esophagus. The acid damages the esophageal mucosa resulting in heartburn, ulcers, bleeding, and scarring, and long term complications such as Barrett's esophagus (pre-cancerous esophageal lining) and adeno-cancer of the esophagus.
Lifestyle advice and antacid therapy are advocated as first line treatment for the disease. However, since most patients with moderate to severe cases of GERD do not respond adequately to these first-line measures and need further treatment, other alternatives including pharmacological, endoscopic, and surgical treatments are employed.
The most commonly employed pharmacological treatment is daily use of H2 receptor antagonists (H2RAs) or proton-pump inhibitors (PPIs) for acid suppression. Since gastro-esophageal reflux disease usually relapses once drug therapy is discontinued, most patients with the disease, therefore, need long-term drug therapy. However, daily use of PPIs or H2RAs is not universally effective in the relief of GERD symptoms or as maintenance therapy. Additionally, not all patients are comfortable with the concept of having to take daily or intermittent medication for the rest of their lives and many are interested in nonpharmacological options for managing their reflux disease.
Several endoscopic procedures for the treatment of GERD have been tried. These procedures can be divided into three approaches: endoscopic suturing wherein stitches are inserted in the gastric cardia to plicate and strengthen the lower esophageal sphincter, endoscopic application of energy to the lower esophagus, and injection of bulking agents into the muscle layer of the distal esophagus. These procedures, however, are not without their risks, besides being technically demanding and involving a long procedure time. As a result, these procedures have largely been discontinued.
Open surgical or laparoscopic fundoplication is also used to correct the cause of the disease. However, surgical procedures are associated with significant morbidity and small but not insignificant mortality rates. Moreover, long-term follow-up with patients treated by surgery suggests that many patients continue to need acid suppressive medication. There is also no convincing evidence that fundoplication reduces the risk of esophageal adenocarcinoma in the long term.
Gastric electrical stimulation (GES) is another therapy aimed at treating both obesity and GERD. GES employs an implantable, pacemaker-like device to deliver low-level electrical stimulation to the gastrointestinal tract. For obesity, GES operates by disrupting the motility cycle and/or stimulating the enteric nervous system, thereby increasing the duration of satiety experienced by the patient. The procedure involves the surgeon suturing electrical leads to the outer lining of the stomach wall. The leads are then connected to the device, which is implanted just under the skin in the abdomen. Using an external programmer that communicates with the device, the surgeon establishes the level of electrical stimulation appropriate for the patient. The Abiliti® implantable gastric stimulation device, manufactured by IntraPace, is currently available in Europe for treatment of obesity.
In another example, Medtronic offers for sale and use the Enterra™ Therapy, which is indicated for the treatment of chronic nausea and vomiting associated with gastroparesis when conventional drug therapies are not effective. The Enterra™ Therapy uses mild electrical pulses to stimulate the stomach. According to Medtronic, this electrical stimulation helps control the symptoms associated with gastroparesis, including nausea and vomiting.
Electrical stimulation has also been suggested for use in the treatment of GERD, wherein the stimulation is supplied to the lower esophageal sphincter (LES). For example, in U.S. Pat. No. 6,901,295, assigned to Endostim, Inc., “A method and apparatus for electrical stimulation of the lower esophageal sphincter (LES) is provided. Electrode sets are placed in the esophagus in an arrangement that induce contractions of the LES by electrical stimulation of the surrounding tissue and nerves. The electrical stimulus is applied by a pulse generator for periods of varying duration and varying frequency so as to produce the desired contractions. The treatment may be short-term or may continue throughout the life of the patient in order to achieve the desired therapeutic effect. The stimulating electrode sets can be used either alone or in conjunction with electrodes that sense esophageal peristalsis. The electrode sets can be placed endoscopically, surgically or radiologically.” The referenced invention relies on sensing certain physiological changes in the esophagus, such as changes in esophageal pH, to detect acid reflux. Once a change in esophageal pH is recognized, the system generates an electrical stimulation in an attempt to instantaneously close the LES and abort the episode of acid reflux. U.S. Pat. No. 6,901,295 is hereby incorporated by reference in its entirety.
Similarly, U.S. Pat. No. 6,097,984, which is incorporated by reference in its entirety, discloses “a system and method for directly stimulating the LES of a patient in order to normally maintain it in a closed state, thereby preventing reflux and treating the symptoms of GERD. The stimulation is inhibited in response to patient swallowing, by monitoring esophageal motility and timing out an inhibition period following detection of motility representative of swallowing. The system utilizes an implanted stimulator which is programmed to deliver a train of stimulus pulses to one or more electrodes fixed around the gastro-esophageal junction and connected to the stimulator by one or more leads. The motility sensing is done by a sensor for sensing mechanical wave movement or electrical signals representative of high motility following swallowing. The motility sensor and stimulating electrodes are attached laparoscopically, and are preferably carried by a common stent carrier which is sutured around the lower esophagus.” In this application, the LES is stimulated to constantly be in a closed state and instantaneously opened when swallowing is detected.
Typically, the leads for GES are implanted in the gastrointestinal wall using a laparoscopic approach. The gastrointestinal musculature is entered through the serosal surface of the stomach. Unfortunately, the use of laparoscopy is not without its risks and is contraindicated in some patients, such as individuals who have adhesions from previous abdominal surgeries. Though it is less invasive than open surgery, laparoscopy still involves tissue incisions for the introduction of the trocars. These incision sites must be sutured closed after the procedure and represent possible infection points. In addition, trocar placement runs the risk of injuring blood vessels, the large bowel, or other organs. Laparoscopy also includes the inherent risk of being converted to open surgery should complications arise during the procedure. Therefore, a need exists for implanting electrical leads in the gastrointestinal tract wall of a patient that is less invasive than current modalities and for those patients for whom laparoscopy is not an option. In addition, laparoscopy is more costly, time consuming, and requires a greater period of patient recovery than less invasive approaches. Therefore, a need exists for a method of implanting electrical leads in the gastrointestinal tract wall of a patient that is also quicker and more cost-effective with less time required for patient healing.